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POSSIBILITIES OF THE USE OF THE VHF-TRANSCEIVER AS A TRANSPONDER IN TRAFFIC SURVEILLANCE SYSTEMS

At present traffic surveillance is mainly operated with primary radar systems, the identification task being fulfilled by the radar controller by way of constant observation of the display unit in conjunction with conducting the radio telephone communications. The position of the ship is determined by evaluation by the land station of the unmodulated transmission signal radiated by the radio set. Position-finding is possible with an unmodified radio set, if, following a request via radio telephone, an operator on board the ship presses the transmitting key. It is possible to automate the position-finding process without major expenditure by effecting some alterations at the radio set. The above position-finding procedure within the 2 m-range is described and examined more closely as to its efficiency and to two possible ways of using it for the purposes of traffic surveillance and/or as navigational aid, respectively. A description is given of the measuring errors to be expected as a function of the location of landbased DF-stations.